Method for the production of aryl-aryl coupled compounds

ABSTRACT

The present invention relates to a process for preparing aryl-aryl-coupled compounds and materials. These materials play an important role in industry, for instance as liquid crystals, pharmaceuticals, agrochemicals and as organic semiconductors. The aryl-aryl couplings hitherto carried out by means of Yamamoto coupling require specific additives in order to give a product suitable for the subsequent use. Particularly in the electronics industry, the Yamamoto coupling needs to meet particular requirements.

The present invention relates to the preparation of aryl-aryl-coupledcompounds and materials. These materials play an important role inindustry, for instance as liquid crystals, pharmaceuticals andagrochemicals, to name only a few fields of application. Particularly inthe fast-growing field of organic semiconductors (e.g. applications inorganic or polymeric light-emitting diodes, organic solar cells, organicICs), these compounds are of great importance.

Various alternative methods are known for the synthesis of suchcompounds, but these do not offer a satisfactory solution, e.g. from atechnical, economic or ecological point of view, in all cases. In manyprocesses, unsatisfactory products or secondary reactions occur, andsuch products have to be separated off and disposed of, which costsmoney, or they cannot be removed and then lead to problems in the use ofthe material.

A particularly important aspect is the efficiency (degree of conversion& selectivity) of the process when it involves a reaction of one or moremultifunctional compound(s). An example of this type of reaction is thereaction of a monofunctional compound with itself, which leads to adiscreet molecule. A further example is a polymerization in which one ormore multifunctional compound(s) is/are reacted with one or more furthermultifunctional compound(s). In many applications of the polymers, ahigh molecular weight is necessary to achieve the desired physicalproperties, e.g. film formation, flexibility, mechanical stability, etc.In the case of organic semiconductors in particular, the electricalproperties are strongly influenced by the molecular weight and a veryhigh molecular weight is usually necessary to avoid, inter alia, defectssuch as short circuits in the electrical device. Furthermore, in thecase of short-chain polymers, the end groups which are inevitablypresent and in this case make up a relatively high proportion, can actas impurities. A high reproducibility of the process is additionallynecessary for this application. The degree of polymerization (DP,average number of repeating units in the chain) of a polymer built up bystepwise growth is related as follows to the degree of conversion of thereaction (p): ${DP} = \frac{1}{1 - p}$

If a high DP is sought, a very efficient reaction is necessary, e.g. ap=0.95 gives DP=20 or a p=0.99 gives a DP=100.

The Yamamoto reaction (T. Yamamoto and A. Yamamoto, Chem. Lett., 1977,353-356, and Japanese patent application JP 02-008213) has proven to bea suitable reaction for preparing aryl-aryl-coupled compounds. This isthe homocoupling of two aromatic halide compounds in the presence of anequimolar amount of a transition metal complex (in general a Ni(0)compound, usually Ni(COD)₂, which is not only expensive but also toxic)in a proton-free environment and under an inert atmosphere. It isgenerally customary for the reaction to be carried out using thesomewhat more expensive but significantly more reactive aryl bromideswhich can readily be synthesized by means of a large number ofbromination reactions. An analogous use of this process forpolymerization is described, for example, in EP-A-1229063 (SumitomoChemicals). Here too, equimolar or even superequimolar amounts of Ni(0)complexes are used, and this is also regarded as necessary.

A number of catalytic variants of the reaction are known, but eachsuffers from restrictions in terms of its economic utility. Reasons forthis are, inter alia, the substrate tolerance, the purificationprocedure, the catalyst system with its necessary ligands and thereaction yield. These studies (cf. EP-A-0012201, EP-A-0025460, WO96/39455, WO 90/06295, WO98/33836) nevertheless form the closest priorart to the present patent application and are incorporated by referenceinto the patent application so that it is not necessary to repeat allthe detailed descriptions given there of the general prior art relatingto Yamamoto reactions.

In the coupling reactions catalyzed by transition metals which have beencarried out by Yamamoto et al. via the Grignard compounds, functionalgroups which are unstable under Grignard conditions, e.g. ketones andesters, have to be avoided in all cases (Japanese patent application JP52-154900). This restriction in respect of the choice of substratelimits the number of useful reactions considerably. A variant of thisprocess using zinc in place of the magnesium has been described.(Japanese patent application JP 61-233014)

The more substrate-tolerant variant of this reaction has been disclosedby Colon et al. (I. Colon and D. R. Kelsey, J. Org. Chem., 51, 1986,2627-2637, European patent-applications EP-A-0025460 and EP-A-0012201).Here, a nickel component is reduced in situ with zinc powder in thepresence of a phosphine (preferably triphenylphosphine) and a bidentateligand to produce an active nickel(0)-phosphine catalyst. Withoutwishing to go into details of the theory of the mechanism, it is assumed(cf., for example, C. A. Tolman, W. C. Seidel and L. W. Gosser, J. Am.Chem. Soc., 96, 1974, 53) that the nickel species loses one or more ofits phosphine ligands in the catalytic cycle and forms coordinatedlyunsaturated complexes. In some of the catalytic substeps, theunsaturated Ni complex species are essential for the reactivity of thearyl halides, but at the same time are the reason for the formation ofundesirable by-products in other substeps. Furthermore, inert complexeswhich no longer display any catalytic activity can be formed from thecoordinatedly unsaturated complexes at high concentrations of thesecomplexes. A second undesirable secondary reaction is the abstraction ofa phenyl group from the phosphine ligand and the resulting, undesirablecoupling with the aryl halides. This reduces the efficiency of thereaction and increases the degree of purification required in order toisolate the desired product. This secondary reaction can be reduced byincreasing the phosphine concentration in the reaction mixture. Theconcentration of the phosphine ligand, preferably triphenylphosphine andsimilar triarylphosphines, should be in the range from 1 to 30equivalents based on the amount of nickel; on the basis of practicalexperience, a concentration window of from 0.1 to 0.5 mol/l for thephosphine ligand is advantageous (at concentrations of from 0.5 to 1mol/l for the aryl halide and from 0.01 to 0.05 mol/l for nickel) forminimizing the two abovementioned effects (cf. Wang et al., WO96/39455). However, the formation of undesirable coupling products isnot suppressed under these conditions and the high phosphine additionsmake costly purification steps necessary afterward.

A bidentate ligand (2,2′-bipyridine, 1,10-phenanthroline, etc.), forinstance 0.2-2 equivalents based on the amount of nickel used, can beadded to the reaction mixture; larger amounts are not described asadvantageous because of its chelating action (Colon et al., J. Org.Chem., 51, 1986, 2627-2637). In addition, a promoter selected from thegroup consisting of alkali metal, alkaline earth metal, zinc, magnesiumand aluminum halides, sulfates and phosphates can be added in an amountof from 1 to 100 equivalents based on the amount of nickel used. Asreducing metal, zinc, magnesium or manganese, preferably the first, isused in equimolar amounts based on the aryl halide.

The Colon variant of the Yamamoto reaction is limited to substrateshaving two substituents in ortho positions relative to the halide;simply ortho-substituted halides likewise display low yields.

In an attempt to minimize the formation of by-products and to solve thepurification problem, further processes have been developed.

In WO 96/39455, Wang et al. describe a coupling process for the reactionof aryl halides (preferably chlorides) or aryl sulfonates to producebiaryls and polyaryls. In this process, a catalyst mixture comprising anickel component, a reducing metal (preferably activated zinc dust) anda phosphite ligand is employed. The ratio of the ligand to the nickel isin the range from 1 to 10 equivalents. However, this process likewisehas a number of weak points, of which a few are mentioned in thefollowing:

Firstly, the phosphite ligands required have to be prepared in acomplicated synthesis and cannot be recovered from the reaction mixtureafter the work-up.

Secondly, the chemical structure of the phosphite ligand has a stronginfluence on the stability of the nickel(0) complexes in the catalyticprocess and has to be optimized afresh for different substrates.

Thirdly, in the case of relatively unreactive starting materials havingelectron-pushing substituents in the ortho or para position, aninterfering secondary reaction, namely the nickel-catalyzed replacementof the halogen by hydrogen, takes place to a greater extent.

Fourthly, the molecular weights M_(w) of the polymer products obtainedcorrespond to a degree of polymerization DP in the order of DP<100.

For the abovementioned reasons, the reaction described is not suitablefor an efficient polymerization process for obtaining high molecularweights and the use of ligands which are not commercially availablerepresents a particular difficulty.

WO 90/06295 of Eastman Kodak describes a process for preparing biarylcomponents from aryl chlorides. The use of bidentate organophosphines asligands is described. The catalyst system further comprises a nickelspecies (in a ratio of 1:3 equivalents to the phosphine ligand) and areducing metal such as zinc or the like in an anhydrous, dipolar,aprotic medium. Equimolar amounts of a nitrogen-containing ligand suchas bipyridine and also inorganic salts in the range from 1 to 100equivalents based on the amount of nickel used can optionally be addedto the phosphorus-containing ligand.

This process, too, has only limited industrial applicability. Onceagain, the bidentate phosphine ligands have to be chosen and preparedsubstrate-specifically. The formation of relatively large amounts of thedehalogenated starting material in the reductive dimerization ofsubstituted aryl halides, on average in the range from 5 to 15%, in somecases up to 60%, may well represent the greatest disadvantage of thisprocess. In addition, isomerically coupled dimers are frequently formed.The preparation of polymeric compounds using this process is notdescribed, and should not succeed because of the abovementionedproblems.

In WO 98/33836, Aiike et al. describe the coupling reaction ofsubstituted sulfonyloxyphenylene with itself or various other monomerswith the aid of a catalyst system which preferably comprises a nickelsalt and a ligand such as triphenylphosphine or 2,2′-bipyridine. Theseligands can be added individually or in combination. As reducing agentin the catalytic system, preference is given to using zinc andmanganese. An inorganic salt such as NaBr, NaI or tetraethylammoniumiodide can be added. However, this patent document is restricted to theabovementioned sulfonyloxyphenylene products.

This critical examination of the prior art makes it clear that there isstill a need for highly efficient processes which lead, at a lowcatalyst concentration, to aryl-aryl-coupled compounds with very fewsecondary reactions. In the interests of clarity, representativeexamples from the abovementioned documents are summarized in thefollowing table. TABLE 1 Literature comparison of known preparativeprocesses. Document 1 Document 2 Document 3 Document 4 EP 12201 WO96/39455 WO 90/06295 WO 96/39455 Starting p-Chloro- 4-Chloro- 2-Chloro-2,5-Dichlor- materials aniline toluene toluene obenzo- phenone SolventDMAC NMP DMF NMP Temperature 80° C. 60° C. 70° C. 90° C. Concentration1.57 mol/l 1.58 mol/l 1.33 mol/l 0.96 mol/l of starting material Molarratio of 1:0.06 1:0.05 1:0.05 1:0.075 starting material to nickelspecies Molar ratio of 1:0.5 1:0.1 1:0.075 1:0.4 starting with twomaterial to phosphorus ligand atoms per ligand Reaction time 1 h 17 h 16h 36 h Yield 88% (GC) 96% (GC) 95% (GC) 92% M_(w) [g/mol] Dimer DimerDimer 14.319

We have now surprisingly found that a particularly efficient Yamamotoprocess is achieved when using Ni(0) complexes which have a specificligand arrangement and a reducing agent together with very small (i.e.catalytic) amounts of Ni.

The invention accordingly provides a process for coupling aromatic orheteroaromatic halogen compounds to form one or more C—C single bonds,characterized in that

-   an Ni(0) complex comprising at least two different ligands, with at    least one ligand being selected from each of the two groups    consisting of heteroatom-containing ligands (group 1) and of π    system ligands (group 2), is used in catalytic amounts, and a    reducing agent which converts consumed nickel back into Ni(0) is    used;-   the reaction takes place in an anhydrous, aprotic medium under a    very largely inert atmosphere,    with the proviso that no phosphorus-containing compound is added.

The reaction according to the invention can (depending on the precisecomposition and temperature) occur either in a single-phase system or amultiphase system, or this can change during the course of the reaction.However, the reaction according to the invention preferably occurs in asingle-phase.

Aryl and heteroaryl compounds are aromatics and heteroaromatics havingfrom 2 to 40 carbon atoms, which can be substituted by one or morelinear, branched or cyclic alkyl or alkoxy radicals which have from 1 to20 carbon atoms and in which one or more nonadjacent CH₂ groups can bereplaced by O, C═O or a carboxy group, substituted or unsubstitutedC2-C20-aryl or -heteroaryl radicals, fluorine, cyano, nitro groups orcan also be unsubstituted.

Simple compounds which are preferably used are the correspondingsubstituted or unsubstituted derivatives of benzene, naphthalene,anthracene, pyrene, biphenyl, fluorene, spiro-9,9′-bifluorene,phenanthrene, perylene, chrysene, naphthacene, pentacene, triptycene,pyridine, furan, thiophene, benzothiadiazole, pyrrole, quinoline,quinoxaline, pyrimidine and pyrazine.

Furthermore, corresponding (in the sense of the above text)multifunctional compounds are expressly also encompassed, and also theoligomers which have functional aryl or heteroaryl ends and occur inpolymerization.

The starting compounds for the process of the invention are aromatic orheteroaromatic halogen compounds of the formula (I),Ar—(X)_(n)  (I)where Ar is an aryl or heteroaryl compound as defined above, X is —Cl,—Br, —I and n is at least 1, preferably from 1 to 20, particularlypreferably 1, 2, 3, 4, 5 or 6, but has a value which is not more thanthe number of aromatic protons which can be present in the startingcompound.

In the case of the preparation of linear polymers, preference is givento n being 2 in all monomers used.

The process of the invention is carried out using Ni(0) complexes. Thesecan either be purchased directly (Ni(COD)₂ and the like) or in-situ fromappropriate precursors or standard solutions, but the catalyst solutionis preferably prepared beforehand.

Precursors which can be used for preparing appropriate Ni(0) complexesare, inter alia, the following Ni compounds: elemental nickel ordisperse or colloidal metallic nickel, supported or unsupported, e.g.nickel sponge, nickel on kieselguhr, nickel on aluminum oxide, nickel onsilica, nickel on carbon, nickel(II) acetate, nickel(II)acetylacetonate, nickel(II) chloride, bromide, iodide, nickel(ii)carbonate, ketonates, formate, sulfate, or complexes which can bederived therefrom, e.g. olefinnickel(II) halides, allylnickel(II)halides, addition compounds of the type NiL₂X₂, where X is chlorine,bromine, iodine and L is an uncharged ligand such as ammonia,acetonitrile, propionitrile, benzonitrile, nickel(II) nitrate,nickel(II) sulfate, nickel(II) oxalate, biscyclooctadienenickel(0),tetrakistriphenylphosphinenickel(0) or further nickel(0) compounds.

As indicated above, the Ni(0) species is preferably prepared beforehandin a catalyst solution. The catalyst solution is generally prepared asfollows:

A reducing agent (e.g. Mn) is mixed with, for example, an Ni(II) salt(e.g. NiBr₂) dissolved in DMF at room temperature under an inertatmosphere. The ligand solution (e.g. bipyridyl and COD dissolved intoluene) is slowly added, and after 5-10 minutes the solution becomesdeep violet. This is stirred vigorously stirred overnight at roomtemperature. The solution is stable for some weeks under suitable, dryprotective gases and is preferably stored and manipulated under aprotective gas atmosphere.

The above-described preparation of an Ni(0) complex solution is likewisesubject matter of the invention.

Ligands used are, as indicated above, firstly ligands from group 1.

These are defined as follows:

-   -   These are generally ligands which have η¹ coordination via a        heteroatom to the nickel. The heteroatoms are preferably        heteroatoms of main group 5 and 6, but with the exception of        phosphorus; they are particularly preferably nitrogen and/or        oxygen. In general, the ligands can be aliphatic compounds        (linear or branched) or aliphatic or aromatic cyclic compounds,        but preferably monocyclic, bicyclic or tricyclic ring systems.    -   However, preference is given to the ligands of group 1 being        bidentate, i.e. having two η¹ coordinations to nickel which are        each via the heteroatoms. This is the case when the ligands are        able to form the bis-η¹-X,Y-coordinated complex fragment shown        in the following scheme, where X and Y are identical or        different and are each preferably nitrogen or oxygen,    -   (where the semicircle depicted represents an alkyl or aryl        bridge described in the text).

Individual examples which may be mentioned are the following:

-   -   1. When X and Y are each nitrogen, this ligand is of the type of        2,2′-bipyridine, 1,10-phenanthroline, 1,1′-bisisoquinoline,        2,2′-biquinoline, 1,8-diazabicyclo[5.4.0]undec-7-ene and the        like. Likewise possible are ligands of the type of, as        illustrated by way of example in the scheme below, pyridines        substituted in the 2 position by methanamine or imidoyl groups,        e.g. α-ethyl-α-methyl-N,N-[diisopropyl]-2-pyridylmethanamine or        2-(N-methylacetimidoyl)pyridine and the like.        -   (R1, R2, R3 and R4 can each be, independently of one            another, for example a hydrogen atom, alkyl or aryl radical,            with the pyridine ring itself also being able to be            substituted further.)    -   2. When X is nitrogen and Y is oxygen, the ligands are, for        example, ligands of the type of the pyridines substituted in the        2 position by 1-alkoxyalkyl or carbonyl groups and shown by way        of example in the following scheme, e.g.        2-(1-methoxy-1-methylethyl)pyridine or 2-acetylpyridine or        2-pyridinecarbaldehyde and the like.        -   (R5, R6 and R7 can each be, for example, a hydrogen atom,            alkyl or aryl radical, where the pyridine ring itself can            also be substituted further.) Ligands of the type of            substituted or unsubstituted 8-alkoxyquinoline are likewise            included.    -   3. When X and Y are each oxygen, the ligands are, for example,        ligands of the type of the furans substituted in the 2 position        by 1-alkoxyalkyl or carbonyl groups and shown in the following        scheme, e.g. 2-(1-ethyl-1-methoxy-propyl)furan or 2-acetylfuran        or 2-furaldehyde and the like.        -   (R8, R9 and R10 can each be, for example, a hydrogen atom,            alkyl or aryl radical, with the furan ring itself also being            able to be substituted further).    -   4. When X is oxygen and Y is nitrogen, these ligands are the        N-alkyl or N-arylimine and -amine derivatives derived from the        above-described ligands and shown by way of example in the        following scheme.        -   (R11, R12, R13 and R14 can each be, independently of one            another, for example a hydrogen atom, alkyl or aryl radical,            with the furan ring itself also being able to be substituted            further.)    -   5. Ligands of the type of vicinal, N- or O-difunctionalized        alkenes as shown by way of example in the following scheme are        therefore likewise possible. R15, R16, R17, R18, R19 and R20 can        each be, independently of one another, for example a hydrogen        atom, alkyl or aryl radical.

Furthermore, ligands from group 2 are used in addition.

These are defined as follows:

-   -   In general, these are ligands which have η² coordination via a π        system to the nickel. The π system is preferably an alkyne,        alkene, η²-coordinated imine or η²-coordinated carbonyl group,        particularly preferably an alkyne or alkene group, very        particularly preferably an alkene group. In general, the        compounds concerned can be aliphatic compounds which are linear,        branched or cyclic, in which some CH₂ groups may also be        replaced by individual heteroatoms (e.g. oxygen, i.e., for        example, ether bridges) and which comprise the appropriate π        system, but are preferably monocyclic, bicyclic or tricyclic        ring systems.    -   However, preference is given to the ligands of group 2 also        being bidentate, i.e. having two η² coordinations to the nickel        which are each via the π systems. This is the case when the        ligands are able to form the bis-η²-A,B-coordinated complex        fragment shown in the following scheme, where A and B are two        identical or different π systems,    -   (where the semicircle depicted represents a bridge described in        the text below).

As bridge, it is possible to employ, for example, the followingstructures:

-   -   1. Relatively short alkyl fragments (linear or branched) which        may also contain individual heteroatoms (e.g. as an ether        group). Preference is given to the π systems being separated        from one another by from one to three, preferably two, CH₂        groups or equivalent bridging units.    -   2. Cyclic systems, for exmaple monocyclic, bicyclic or tricyclic        ring systems having from 6 to 14 carbon atoms of which        individual carbon atoms can, as described above, be replaced by        heteroatoms. Very particularly useful cyclic systems are        substituted or unsubstituted rings selected from among the types        of compounds 1,4-cyclohexadiene, norbornadiene,        bicyclo[2.2.2]octa-1,4-diene, 1,4-cycloheptadiene,        1,5-cyclooctadiene, 0,1,5-cyclononadiene, various cis- or        trans-decalin-dienes, for example cyclooctadiene derivatives.

The invention provides for at least one ligand from the 1st group and atleast one ligand from the 2nd group to be present in the active Ni(0)complexes used. In the process of the invention, the Ni(0) compound isused in catalytic amounts. This means that less than 50 mol % of Nicompound (based on the amount of halide), preferably less than 5 mol %,in the case of dimerization reactions very particularly preferably lessthan 3 mol %, is used. However, to achieve a satisfactory reaction ratein polymerizations, it is advisable to use an Ni(0) concentration whichis not too low. Thus, 5 mol % of Ni compound is an appropriate lowerlimit in polymerizations.

To carry out the process of the invention, it is necessary to have, asdescribed above, a reducing agent which reduces “consumed” nickel(II)back to Ni(0). Possible reducing agents are all elements or compounds ofthe electrochemical series having a redox potential which is morenegative than that of Ni²⁺ (−0.257 V), preferably aluminum, manganese,iron, zinc, sodium, calcium, magnesium, very particularly preferablymanganese powder having a purity of 99.99%. It is likewise possible touse more complex reducing agents such as metal hydrides, hydrazine andfurther organic and inorganic reducing agents.

This reducing agent is used in a stoichiometric ratio (based on theamount of halide) in the range from 0.5 to 10 equivalents, veryparticularly preferably in the range from 2 to 6 equivalents.

The process of the invention preferably takes place in solution. In thecase of suitable reactants (i.e. ones where both the starting materialsand the products or the mixture of starting material and product areliquid in the chosen reaction range [p, T]), the starting material(s)can itself/themselves serve as solvent.

Suitable solvents are inert, aprotic solvents, preferably relativelynonpolar solvents such as aliphatic and aromatic hydrocarbons, e.g.pentane, cyclohexene, toluene, xylene and the like, or saturated,open-chain or cyclic ethers, e.g. diethyl ether or tetrahydrofuran,particularly preferably aromatic hydrocarbons, very particularlypreferably toluene. These can be mixed with inert, dipolar solvents suchas N,N′-dimethylformamide, N,N′-dimethylacetamide,N-methylpyrrolidin-2-one, tetramethyl-urea, dimethyl sulfoxide orsulfolane and the like in any mixing ratio, for example in theparticularly useful mixture of DMF and toluene in a DMF:toluene ratio of≦1:20. The process of the invention using the catalytic amountsdescribed gives the good yields reported in the examples below whenoxygen and protic compounds, in particular water and alcohols, are verysubstantially excluded.

It is therefore advantageous to keep the oxygen content in the reactionatmosphere below 1%, preferably below 1000 ppm, particularly preferablybelow 10 ppm, very particularly preferably below 1 ppm.

An analogous situation applies to protic compounds (for example water).

These reaction conditions are achieved, in particular, by carrying outthe reaction under an appropriate oxygen-free or low-oxygen protectivegas such as argon or nitrogen, preferably argon, or saturating thesolvent(s) and reactants with this gas beforehand. This is preferablyachieved by multiple degassing of the solvents and/or passing protectivegas through the solvent.

To avoid protic impurities and water or to bring the content to theabovementioned values, use is either made of appropriate grades or thesolvents are dried or purified by appropriate literature methods (cf.,for example, “Purification of Laboratory Chemicals”, 2^(nd) Edition,Pergamon Press Ltd., 1980).

The reaction should then preferably be carried out in suitableapparatuses, very particularly preferably in apparatuses which havepreviously been flushed well with dry protective gas, e.g. argon.

The starting materials, the reaction mixture and the products shouldpreferably be stored, processed and manipulated under a protective gasatmosphere; this applies very especially to the reagents manganese andbipyridine and the reagents corresponding to these, and also naturallyto any catalyst solution prepared beforehand from these. The sameapplies to the solutions of the polymers synthesized. If the process iscarried out on a laboratory scale, it can be useful to work in a glovebox.

The process of the invention is generally only slightly exothermic andusually requires gentle activation. The process is therefore frequentlycarried out at temperatures above room, temperature. A preferredtemperature range is therefore the range from room temperature to theboiling point of the reaction mixture, particularly preferably thetemperature range from 40 to 120° C., very particularly preferably therange from 40 to 60° C. However, it is also possible that the reactionproceeds sufficiently rapidly even at room temperature, so that noactive heating is required.

The reaction is carried out with stirring, and simple stirrers orhigh-viscosity stirrers can be employed depending on the viscosity ofthe reaction mixture. In the case of high viscosities, baffles can alsobe used.

The concentration of the reaction components depends very much on therespective reaction. While polymerizations are usually (because of theviscosity increase which occurs in this case) carried out atconcentrations in the range below 0.5 mol/l (based on C—C bonds to beformed), a higher concentration range can be employed in the synthesisof defined individual molecules.

The reaction time can in principle be chosen freely and is adapted tothe respective reaction rate. An industrially appropriate range is froma few minutes to 120 hours, in the case of dimerization reactionspreferably from 60 minutes to 48 hours, but can exceed these values inthe case of relatively unreactive starting materials or sluggishpolymerization reactions.

In principle, the reaction proceeds under atmospheric pressure. However,under industrial conditions, it can be advantageous to work undersuperatmospheric or subatmospheric pressure. This depends very much onthe individual reaction and on the available equipment.

The advantages of the novel process described are, inter alia, thefollowing:

Excellent efficiency (degree of conversion), as a result of whichmaterials which have very few flaws resulting from secondary reactionsare obtained. Particularly in the case of multifunctional compounds, theprocess of the invention is advantageous since the efficiency is then ofgreat importance. Especially in the case of polymerizations in which thestarting materials have, in the case of linear polymers, two reactivegroups and the multiple successive aryl-aryl coupling leads to theformation of a chain molecule, the products of the process of theinvention display extraordinarily high chain lengths and molecualrweights.

A particular advantage of the present invention is that, owing to theimproved efficiency of the Yamamoto reaction in the polymerization, theamount of Ni(0) compound used can nevertheless be kept smaller. Thisresults in the process being both economically and ecologicallyadvantageous and, in addition, the residual amount of nickel in theproduct being lower. This brings technical advantages, e.g. avoidance ofdiscoloration of the product, but the reduction in the amount of suchimpurities is particularly advantageous in the case of organicsemiconductors since the presence of metal residues leads to adverseeffects in use. In general, it is possible to bring the residual nickelcontent to below 1000 ppm, usually below 100 ppm and very frequentlybelow 10 ppm or even below 1 ppm, by means of simple purificationprocedures. This is an outstanding feature of the process of theinvention, since it clearly distinguishes the products produced in thisway from the prior art.

In addition, appreciable contamination by the waste products of theP-containing ligands is, in particular, avoided in the process of theinvention. The avoidance of the known, complicated purificationprocedures when using P-containing ligands represents a further decisiveimprovement over the prior art achieved by the process of the invention.In particular, the avoidance of these P-containing ligands leads to noP-containing impurities (originating from the ligands) being present inthe product. This applies especially in the case of polymers, sinceprocesses of the prior art frequently lead to such phosphine-containinggroups being transferred into the polymer (as end groups) and in thisway avoiding removal in the purification. The polymers obtained by theprocess of the invention are thus distinguished from the prior art bythe fact that they are free of phosphorus. The phosphorus content of thepolymer is less than 10 ppm, preferably less than 1 ppm.

The isolation of the product from the reaction mixtures is, according tothe invention, preferably carried out, as in the representative examplesbelow, by filtration of the reaction mixture through Celite andsubsequent extraction with 1M HCl or other suitable work-up methods. Theproducts produced can then be purified further by standard methods suchas recrystallization, distillation under atmospheric or subatmosphericpressure, precipitation or reprecipitation, chromatography, sublimationand the like.

Since the process of the invention has, as described above, a very highefficiency, a preferred embodiment is the conversion of multifunctionalmolecules into polymers. For the purposes of the present patentapplication, multifunctional means that a compound has a plurality of(e.g. two, three, four, five, etc.) identical or similar functionalunits which all react in the same way to form a product molecule in thereaction in question (here the Yamamoto reaction). The reaction ofmultifunctional compounds is here primarily the reaction to form aproduct having polymeric character. This too is expressly a Yamamotoreaction for the purposes of the present invention.

Polymeric character, according to the present invention, is present whenthe decisive properties (e.g. solubility, melting point, glasstransition temperature, etc.) do not change or change onlyinsignificantly on addition or omission of a single repeating unit. Asimpler definition is provided by the degree of polymerization DP,according to which “polymeric character” is then defined as a degree ofpolymerization in the order of DP>100; below this, the compounds areregarded as oligomers.

The polyarylenes (in the present context, this term also encompassescopolymers comprising additional non-arylene or non-heteroarylene unitsin the main chain) produced using the process of the invention arecharacterized by a high molecular weight (which can also be set in acontrolled fashion) and the absence (or very small proportion) ofstructural defects produced by the polymerization. The process of theinvention makes it possible to obtain polyarylenes having a DP ofgreater than 100, preferably greater than 200, in particular 300.

These polymers produced by the process of the invention therefore offersignificant improvements over the prior art and are thus likewisesubject matter of the invention.

As described above, a further preferred embodiment of the process of theinvention is its use for coupling monofunctional compounds.

The dimeric compounds produced in this way are characterized by theabsence (or very small proportion) of structural defects produced by thereaction, e.g. positional isomers or hydrodehalogenation products.

These compounds produced by the process of the invention therefore offersignificant improvements over the prior art and are thus likewisesubject matter of the invention. The particular insensitivity of theprocess described to substituent effects makes the use of asubstantially larger number of starting materials possible. Theseinclude starting materials having substitution patterns which havehitherto not been able to be coupled by Yamamoto reactions (e.g. doublyortho-substituted aryl halide).

A preferred process according to the invention (dimerization orpolymerization) can be described as follows:

The reaction apparatus is firstly dried, the chosen solvent (e.g.toluene) is then degassed and blanketed with argon.

The prepared catalyst mixture is mixed with the reducing agent, e.g.manganese, and stirred under argon at, for example, 50° C.

The starting materials (monomers) are dissolved in a suitable solvent,e.g. toluene, and the reaction is started by addition of the startingmaterial solution to the catalyst solution.

If appropriate, small amounts of monofunctional compounds (“endcappers”) or trifunctional or multifunctional groups (“branchers”) areadded.

The reaction is maintained at the reaction temperature while stirringvigorously and is carried out over a period of about 48-120 hours.

It has been found to be advantageous to carry out end capping at the endof the reaction, i.e. to add monofunctional compounds which cap anyreactive end groups in the polymers.

At the end of the reaction, the polymer can then be purified further bycustomary purification methods such as precipitation, reprecipitation,extraction and the like. For use in highly demanding applications (e.g.polymeric light-emitting diodes), contamination with organic substances(e.g. oligomers) and inorganic substances (e.g. Ni residues, residues ofthe reducing agent) generally has to be brought to a very low level. Inthe case of Ni and metallic reducing agents, this can be achieved invarious ways, e.g. by means of ion exchangers, liquid-liquid extraction,extraction with complexing agents and other methods, while the removalof low molecular weight material can occur, for example, by solid-liquidor liquid-liquid extraction or by multiple reprecipitation,

and the removal of further inorganic impurities can occur, for example,by the methods described above for nickel and the low molecular weightmaterial and also by extraction with, for example, mineral acids.

The process described here makes it possible to prepare, for example,polyarylenes as described in EP-A-842.208, WO 00/22026, WO 00/46321, WO99/54385, WO 00/55927, WO 97/31048, WO 97/39045, WO 92/18552, WO95/07955, EP-A-690.086 and the as yet unpublished applications DE10114477.6 and DE 10143353.0 particularly efficiently. The polymersprepared by the process of the invention frequently display advantagesover those reported in this cited literature: for example in respect ofthe freedom from defects, the molecular weight, the molecular weightdistribution and thus frequently also in respect of the respective useproperties.

The invention thus also provides poly(arylenes) which are characterizedin that they have been prepared by the process described above and havea particularly low occurrence of defects, in particular ofpoly(arylenes), which have a phosphrus content of less than 10 ppm.

The polymers of the invention can be used in electronic components suchas organic light-emitting diodes (OLEDs), organic integrated circuits(O-ICs), organic field effect transistors (OFETs), organic thin filmtransistors (OTFTs), organic solar cells (O-SCs), organic laser diodes(O-lasers), organic color filters for liquid crystal displays or organicphotoreceptors. These uses are likewise subject matter of the presentinvention.

The invention described is explained by the description and the examplesgiven below, but is not in any way restricted to these. Rather, a personskilled in the art will naturally easily be able to apply theinformation provided to the systems listed above and those described inthe literature cited.

EXAMPLES OF THE PROCESS OF THE INVENTION Example V1 Preparation of theCatalyst Solution

Manganese (0.11 g, 2 mmol) was mixed at room temperature with NiBr₂ (200mg, 0.9 mmol) dissolved in DMF (5 ml). The ligand solution consisting of150 mg (0.96 mmol) of bipyridine and 0.12 ml (1.0 mmol) of COD dissolvedin 15 ml of toluene) was slowly added, and the solution became deepviolet after 5-10 minutes. The mixture was stirred vigorously at roomtemperature for one night. This solution was stable for some weeks underargon.

A1: Preparation of Dimeric, Multifunctional Compounds

Example D1

Manganese (1.6 g, 30 mmol) and the catalyst solution (11 ml) werestirred at 50° C. for 10 minutes under argon. The mixture had a stableviolet color. 2-bromotoluene (3.4 g, 20 mmol) in 50 ml of toluene wasthen added, and the reaction mixture turned red. The reaction mixturewas stirred at 50° C. for 48 hours (until the solution became violetagain). The mixture was then cooled to room temperature, filteredthrough Celite and evaporated on a rotary evaporator. The residue wasdissolved in CH₂Cl₂ and washed with 1M HCl (100 ml) and water. Theorganic phase was dried over Na₂SO₄, filtered and evaporated on a rotaryevaporator. Chromatography (silica gel, eluent:hexane) gave 1.7 g(yield: 94%) of the desired product (D1) which according to HPLC had apurity of 99.9%.

¹H NMR (CDCl₃): 7.41 ppm (m, 4H); 7.37 ppm (m, 2H); 7.27 ppm (dd, 2H),2.23 ppm (s, 6H);

HPLC: 95% MeOH/THF (9:1)+5% of water; 1 ml/min, Stablebond SB-C18; 3.5μm; 4.6×75 mm, 40° C., UV/VIS detection.

Example D2

Variation 1:

Manganese (0.3 g, 5.4 mmol) and the catalyst solution (1 ml) was stirredat 50° C. for 10 minutes under argon. The mixture had a stable violetcolor. The starting material (1.01 g, 2 mmol) was then added as asolution in 10 ml of toluene, and the reaction mixture turned deep red.The reaction mixture was stirred at 50° C. for 48 hours. The mixture wasthen cooled to room temperature, filtered through Celite and evaporatedon a rotary evaporator. The residue was dissolved in CH₂Cl₂ and washedwith 1M HCl (100 ml) and water. The organic phase was dried over Na₂SO₄,filtered and evaporated on a rotary evaporator.

This gave 820 mg (yield: 96%) of the desired product (D2) whichaccording to HPLC had a purity of 98%, and also 2% of debrominatedstarting material.

¹H NMR (CDCl₃): 7.79 (2H, d, J=7.34 Hz); 7.74 (2H, d, J=7.98 Hz); 7.69(4H, d, J=7.93 Hz); 7.30-7.38 (8H, m); 7.05 (2H, dt, J=7.91 Hz, J=1.03);6.87 (2H, d, J=1.39 Hz); 6.67 (2H, d, J=7.61 Hz); 6.62 (4H, d, J=1.39Hz); 1.10 (36H, s).

¹³C NMR (CDCl₃): 150.68, 150.04, 149.91, 148.90, 141.20, 140.86, 140.66,139.24, 127.60, 127.35, 126.72, 124.74, 124.09, 122.55, 120.61, 119.83,119.78, 119.05, 66.29, 34.74, 31.37.

Variation 2:

Manganese (0.3 g, 5.4 mmol) and the starting material (1.01 g, 2 mmol)dissolved in 10 ml of toluene were stirred at 50° C. for 10 minutesunder argon. The violet catalyst solution (1 ml) was added. The reactionmixture became deep red. Further observations are analogous to variant1.

Variation 3:

Manganese (0.33 g, 6 mmol) was mixed at room temperature with NiBr₂ (20mg, 0.09 mmol) dissolved in DMF (0.5 ml). The ligand solution (15 mg(0.096 mmol) of bipyridyl and 0.012 ml (0.1 mmol) of COD dissolved in1.5 ml of toluene) was added slowly, and after 5-10 minutes the solutionbecame deep violet. The mixture was stirred vigorously at roomtemperature for one night. The starting material (2.03 g, 4 mmol) wasthen added as a solution in 10 ml of toluene, and the reaction mixtureturned deep red. Further observations analogous to variant 1.

Example D3

Manganese (1.04 g, 18.9 mmol) and the catalyst solution (8.75 ml) werestirred at 50° C. for 10 minutes under argon. The mixture had a stableviolet color. The starting material (4.54 g, 12.9 mmol) dissolved in 35ml of toluene was then added, and the reaction mixture became deep red.The reaction mixture was stirred at 50° C. for 48 hours. The mixture wasthen cooled to room temperature, filtered through Celite and evaporatedon a rotary evaporator. The residue was dissolved in CH₂Cl₂ and washedwith 1M HCl (100 ml) and water. The organic phase was dried over Na₂SO₄,filtered and evaporated. The product was recrystallized from ethanol.

This gave 3.16 g (yield: 90%) of the desired product (D3) whichaccording to HPLC had a purity of 99.9%.

¹H NMR (CDCl₃): 7.37 (4H, m); 7.20-6.90 (20H, m); 2.3 (12H, s).

A2: Preparation of Polymers

The preparation of appropriate monomers is described, inter alia, in theabovementioned unpublished applications DE 10114477.6 and DE 10143353.0;these are hereby incorporated by reference into the present invention.

Example P1 Copolymerization of 50 mol % of2,7-dibromo-2′,3′,6′,7′-tetra(2-methylbutyloxy)spirobifluorene (M1), 40mol % of2,7-dibromo-9-(2′,5′-dimethyl-phenyl)-9-[3″,4″-bis(2-methylbutyloxy)phenyl]fluorene(M2), 10% ofN,N′-bis(4-bromophenyl)-N,N′-bis(4-tert-butylphenyl)benzidine (M3)(Polymer P1).

Manganese (440 mg, 8 mmol) and the catalyst solution (2 ml) were stirredat 50° C. for 10 minutes under argon. The mixture was a stable violetcolor. The monomers (655 mg (0.8 mmol) of M1,433 mg (0.64 mmol) of M2,121 mg (0.16 mmol) of M3) were then added as a solution in 20 ml oftoluene, and the reaction mixture turned red. The reaction mixture wasstirred at 50° C. for 5 days. The mixture was then cooled to roomtemperature, diluted with 10 ml of toluene and filtered through Celite.The organic phase was washed 3× with HCl (50 ml) and with H₂O andprecipitated by introducing it dropwise into 500 ml of methanol. Thepolymer was dissolved in 50 ml of toluene, precipitated with 500 ml ofMeOH, washed and dried under reduced pressure. The polymer was extractedwith a 1/1 mixture of THF/MeOH in a Soxhlet extractor for 48 hours. Thepolymer was dissolved in 50 ml of toluene and reprecipitated once morein 500 ml of methanol, filtered off with suction and dried to constantmass. This gave 0.8 g (yield: 84%) of the polymer P1 as a solid.

¹H NMR (CDCl₃): 7.8-7.7 (m, 1H, spiro); 7.7-7.1 (m, 10.7H, fluorene,spiro, TAD); 6.6 (br. s, 0.8H, fluorene), 6.21 (m, 1H, spiro); 4.0-3.4(3×m, 5.6H, OCH₂), 2.16 (s, 1.2H, CH₃); 1.9-0.7 (m, alkyl H, includingt-butyl at 1.30).

GPC: THF; 1 ml/min, Pigel 10 μm Mixed-B 2×300×7.5 mm², 35° C., R1detection: M_(w)=276400 g/mol, M_(n)=73500 g/mol.

The residual metal contents were also determined by ICP-AES-MS:

-   nickel<3 ppm, manganese<5 ppm (in each case below the detection    limit).

Further polymers were prepared in a manner analogous to the descriptionsfor P1. The molecular weights M_(w) and M_(n) are summarized in thefollowing table.

M1

M2

M3

M4

M5 Proportion of monomers in the polymerization [%] GPC* M_(w) M_(n)(1000 (1000 Polymer M1 M2 M3 M4 M5 g/mol) g/mol) P1 50 40 10 276 73 P270 10 20 738 66 P3 80 10 10 245 75 P4 70 10 20 559 165 P5 50 50 270 55*GPC: THF; 1 ml/min, Pigel 10μm Mixed-B 2 × 300 × 7.5 mm², 35° C., RIdetection

1. A process for coupling aromatic or heteroaromatic halogen compoundsto form one or more C—C single bonds, characterized in that an Ni(0)complex comprising at least two different ligands, with at least oneligand being selected from each of the two groups consisting ofheteroatom-containing ligands (group 1) and of π system ligands (group2), is used in catalytic amounts, and a reducing agent which convertsconsumed nickel back into Ni(0) is used; the reaction takes place in ananhydrous, aprotic medium under a very largely inert atmosphere, withthe proviso that no phosphorus-containing compound is added.
 2. Theprocess as claimed in claim 1, characterized in that it occurs in asingle phase.
 3. The process as claimed in claim 1, characterized inthat the aromatic or heteroaromatic halogen compounds are aromatics orheteroaromatics having from 2 to 40 carbon atoms, which can besubstituted by one or more linear, branched or cyclic alkyl or alkoxyradicals which have from 1 to 20 carbon atoms and in which one or morenonadjacent CH₂ groups can be replaced by O, C═O or a carboxy group,substituted or unsubstituted C2-C20-aryl or -heteroaryl radicals,fluorine, cyano, nitro groups or can also be unsubstituted.
 4. Theprocess as claimed in claim 3, characterized in that the aromatics orheteroaromatics are substituted or unsubstituted derivatives of benzene,naphthalene, anthracene, pyrene, biphenyl, fluorene, spiro,9,9′-bifluorene, phenanthrene, perylene, chrysene, naphthacene,pentacene, triptycene, pyridine, furan, thiophene, benzothiadiazole,pyrrole, quinoline, quinoxaline, pyrimidine or pyrazine.
 5. The processas claimed in claim 1, characterized in that the catalyst is preparedbeforehand.
 6. The process as claimed in claim 1, characterized in thatthe catalyst is prepared in situ.
 7. A process for preparing an Ni(0)complex as claimed in claim 1, characterized in that a reducing agent ismixed with an Ni(II) salt dissolved in DMF at room temperature, a ligandsolution in toluene is slowly added and the mixture is stirredvigorously.
 8. The process as claimed in claim 1, characterized in thatthe ligands of group 1 contain heteroatoms from main group 5 or 6, withthe exception of phosphorus.
 9. The process as claimed in claim 8,characterized in that the ligands contain nitrogen and/or oxygen. 10.The process as claimed in claim 8, characterized in that the ligandshave two η¹ coordinations to the nickel, in each case via theheteroatoms.
 11. The process as claimed in claim 1, characterized inthat the ligands of group 2 have at least one η² coordination via a πsystem to the nickel.
 12. The process as claimed in claim 11,characterized in that these ligands comprise alkyne or alkene groups.13. The process as claimed in claim 11, characterized in that theseligands have two η² coordinations to the nickel, in each case via the πsystems.
 14. The process as claimed in claim 1, wherein relativelynonpolar solvents serve as solvent.
 15. The process as claimed in claim14, characterized in that pentane, cyclohexene, toluene or xylene serveas solvent.
 16. The process as claimed in claim 14, characterized inthat these solvents are mixed with inert, dipolar solvents.
 17. Theprocess as claimed in claim 16, characterized in that a mixture of DMFand toluene is used.
 18. A polyarylene which has a phosphorus content ofless than 10 ppm and is obtainable by a process as claimed in claim 1.19. The process as claimed in claim 1, wherein said nonpolar solvent isan aliphatic and aromatic hydrocarbon.
 20. The process as claimed inclaim 15, characterized in that these solvents are mixed with an inert,dipolar solvent and said dipoloar solvent is N,N′-dimethylformamide,N,N′-dimethylacetamide, N-methylpyrrolidin-2-one, tetramethylurea,dimethyl sulfoxide or sulfolane.